Ali Shahin S, Melnick Rachel L, Crozier Jayne, Phillips-Mora Wilberth, Strem Mary D, Shao Jonathan, Zhang Dapeng, Sicher Richard, Meinhardt Lyndel, Bailey Bryan A
Sustainable Perennial Crops Laboratory, Plant Sciences Institute, USDA/ARS, Beltsville Agricultural Research Center-West, Beltsville, MD, 20705, USA.
Mol Plant Pathol. 2014 Sep;15(7):698-710. doi: 10.1111/mpp.12126. Epub 2014 Apr 14.
An understanding of the tolerance mechanisms of Theobroma cacao used against Moniliophthora roreri, the causal agent of frosty pod rot, is important for the generation of stable disease-tolerant clones. A comparative view was obtained of transcript populations of infected pods from two susceptible and two tolerant clones using RNA sequence (RNA-Seq) analysis. A total of 3009 transcripts showed differential expression among clones. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis of differentially expressed genes indicated shifts in 152 different metabolic pathways between the tolerant and susceptible clones. Real-time quantitative reverse transcription polymerase chain reaction (real-time qRT-PCR) analyses of 36 genes verified the differential expression. Regression analysis validated a uniform progression in gene expression in association with infection levels and fungal loads in the susceptible clones. Expression patterns observed in the susceptible clones diverged in tolerant clones, with many genes showing higher expression at a low level of infection and fungal load. Principal coordinate analyses of real-time qRT-PCR data separated the gene expression patterns between susceptible and tolerant clones for pods showing malformation. Although some genes were constitutively differentially expressed between clones, most results suggested that defence responses were induced at low fungal load in the tolerant clones. Several elicitor-responsive genes were highly expressed in tolerant clones, suggesting rapid recognition of the pathogen and induction of defence genes. Expression patterns suggested that the jasmonic acid-ethylene- and/or salicylic acid-mediated defence pathways were activated in the tolerant clones, being enhanced by reduced brassinosteroid (BR) biosynthesis and catabolic inactivation of both BR and abscisic acids. Finally, several genes associated with hypersensitive response-like cell death were also induced in tolerant clones.
了解可可树针对霜霉果腐病的病原菌——可可毛色二孢菌的耐受机制，对于培育稳定的抗病克隆体至关重要。通过RNA序列（RNA-Seq）分析，对两个感病克隆体和两个抗病克隆体的感染豆荚转录本群体进行了比较观察。共有3009个转录本在克隆体间表现出差异表达。对差异表达基因进行的京都基因与基因组百科全书（KEGG）通路分析表明，抗病和感病克隆体之间有152条不同的代谢通路发生了变化。对36个基因进行的实时定量逆转录聚合酶链反应（实时qRT-PCR）分析验证了差异表达。回归分析证实，感病克隆体中基因表达与感染水平和真菌载量呈一致的变化趋势。在感病克隆体中观察到的表达模式在抗病克隆体中有所不同，许多基因在低感染水平和真菌载量时表达较高。对表现出畸形的豆荚进行实时qRT-PCR数据的主坐标分析，区分了感病和抗病克隆体之间基因的表达模式。虽然有些基因在克隆体间组成性地差异表达，但大多数结果表明，抗病克隆体在低真菌载量时诱导了防御反应。几个诱导子响应基因在抗病克隆体中高表达，表明能快速识别病原体并诱导防御基因。表达模式表明，茉莉酸-乙烯和/或水杨酸介导的防御途径在抗病克隆体中被激活，通过降低油菜素内酯（BR）生物合成以及BR和脱落酸的分解代谢失活而增强。最后，几个与过敏反应样细胞死亡相关的基因在抗病克隆体中也被诱导。
